System and method for inertial torque reaction management

ABSTRACT

A system and method for managing inertial torque reactions on stationary powertrain structure rotate at least one selected engine component and at least one selected drive train component in opposite directions so the rotational inertia of the selected drive train component acts in a direction opposite to that of the rotational inertia of the selected engine component to reduce or eliminate the inertial torque reactions on stationary powertrain structure caused by rotational acceleration and deceleration of powertrain components and improves performance with respect to noise, vibration, and harshness (NVH).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and methods for managing inertial torque reaction of rotating machines.

2. Background Art

A conventional powertrain has a “stationary” structure that is attached to the vehicle chassis with resilient mounts. In conventional powertrains, rotating inertia of various engine and transmission components including the crankshaft, flywheel, and torque converter of an automatic transmission, for example, is rotated in the same direction, having a compounding effect. When a compression or combustion event of the engine causes an acceleration of the rotating inertia, generally, there is an equal but opposite inertial torque reaction imposed upon the stationary structure. As such, the stationary structure is not truly stationary, but instead, vibrates in opposition to the accelerations of the rotating inertia. This vibration of the stationary structure passes vibration through the resilient mounts into the vehicle chassis, and may result in unwanted noise and vibration within the vehicle passenger compartment.

Conventional solutions to this vibration issue include controlling the engine operating conditions to minimize the magnitude and frequency range of the inertial torsional vibrations and tuning the powertrain mounts to minimize transmission of vibrations. However, the constraints placed on the engine/powertrain operation may impact the ability to achieve other desirable operating characteristics relative to responsiveness, fuel economy, and/or emissions, for example.

Other known solutions control one or more counter-rotating elements to reduce or eliminate inertial torque reaction, such as disclosed in U.S. Pat. Nos. 5,551,928, and 5,570,615, for example. While these approaches may reduce the torque reaction on the powertrain structure, the increased mass also increases weight and reduces responsiveness of the system.

SUMMARY OF THE INVENTION

The present invention includes a system and method for managing inertial torque reaction by rotating inertial powertrain or drivetrain components a direction opposite to the rotation of engine/motor inertial components, to reduce or eliminate torque reaction on stationary powertrain components.

In one embodiment, the present invention uses a device to provide counter-rotation of one or more engine/motor components relative to rotating transmission or transaxle components to reduce or eliminate the inertial torque reaction otherwise associated with angular acceleration/deceleration of a rotating mass on stationary structure or mounting components. The device may be implemented by a plurality of drive components such as gears, belts, chains and sprockets, or any similar device used to couple an output component of an internal combustion engine to one or more components of the powertrain, such as the torque converter of an automatic transmission or the generator of a hybrid powertrain. The device causes one or more inertial powertrain components to rotate in a direction opposite to that of various engine inertial components, such as a crankshaft. The effective inertia of the counter rotating components may be substantially matched to that of the forward rotating components using a device with an appropriate input/output ratio to create a speed differential between the counter rotating engine/motor components and the forward rotating powertrain components, or by adjusting the mass or component geometry of engine or powertrain components, for example.

In a transversely mounted internal combustion engine and transaxle, as generally used in, but not limited to, front wheel drive (FWD) vehicles, for example, the crankshaft and the torque converter may be connected using toothed wheels enabling the torque converter and crankshaft to rotate in opposite directions. A separate or integrated device may be used to reduce or eliminate backlash and associated noise, such as a scissors gear, for example. The opposing direction of rotation of the crankshaft and torque converter reduces or eliminates the inertial torque reaction on the stationary powertrain structure to reduce or eliminate unwanted vibration and noise.

A longitudinally mounted engine and transmission application, as generally used in, but not limited to, rear wheel drive (RWD) vehicles, for example, may incorporate a simple planetary gear set to connect the crankshaft to the torque converter. Such a planetary gear set typically includes a sun gear, a ring gear, and a carrier with a plurality of pinions that are constantly in mesh with the sun and ring gears. In such an arrangement, for example, the carrier may be rendered stationary by using a plurality of fasteners to connect it with the engine/motor block. The sun gear of the planetary gear set may be connected to the crankshaft using any of a variety of methods including using conventional fasteners or alternatively splines with at least one retaining ring. Likewise, the ring gear or the annulus of the planetary gear set may be connected to the engine/motor flex plate using a plurality of fasteners. Such an arrangement allows the ring gear to rotate in a direction opposite to that of the sun gear when the carrier is non-rotating. Thus, at least one drivetrain component, such as the torque converter, will rotate in a direction opposite to that of the crankshaft and create corresponding rotational inertia to reduce or eliminate the inertial torque reaction otherwise associated with a change in angular acceleration/deceleration of rotating components of the engine on the stationary powertrain structure reducing or eliminating associated noise and vibration.

The present invention provides a number of advantages. For example, the present invention provides systems and methods for managing inertial torque reaction by providing a counter-rotating inertia generated by conventional powertrain components to reduce or eliminate the torque reaction on the powertrain structure and improve performance with respect to noise, vibration, and harshness (NVH). Reversing rotation of conventional powertrain components obviates the need for additional components or mass to generate balancing inertia. This reduces any adverse impact on powertrain weight, responsiveness, and overall performance relative to conventional solutions that add components solely for balancing or canceling torque reactions associated with rotating inertia.

The present invention may allow variable displacement engines to idle and drive at low engine speeds with fewer than all of the cylinders firing without unacceptable NVH. Also, the reduced or limited inertial torque reaction on the stationary powertrain structure should reduce noise, vibration, and harshness (NVH) with the uneven firing intervals that occur when an 8-cylinder engine operates in a reduced or variable displacement mode with 3, 5, 6, or 7 firing cylinders, for example.

The above advantage and other advantages and features of the present invention will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view block diagram illustrating a system or method for managing inertial torque reaction of a transversely mounted powertrain according to one embodiment of the present invention;

FIG. 2 is a top view block diagram illustrating another device for coupling a torque converter to an engine or motor in a system or method for managing inertial torque reaction according to the present invention;

FIG. 3 is a side view block diagram of the system illustrated in FIG. 2;

FIG. 4 is a top view block diagram illustrating a system or method for managing inertial torque reaction for a longitudinally mounted powertrain according to one embodiment of the present invention;

FIG. 5 is a cross-section of a device for coupling a drivetrain to an engine in a system or method for managing inertial torque reaction according to one embodiment of the present invention; and

FIG. 6 is a block diagram illustrating a system or method for managing inertial torque reaction in a hybrid engine/motor powertrain according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

As those of ordinary skill in the art will understand, various features of the present invention as illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce embodiments of the present invention that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present invention may be desired for particular applications or implementations.

Referring now to FIG. 1, a block diagram illustrating a representative embodiment of the present invention in a transversely mounted powertrain application is shown. As those of ordinary skill in the art will appreciate, transversely mounted powertrains are typically used in front wheel drive (FWD) vehicles. However, as described herein, the present invention is not limited to conventional vehicular applications and may be used in various types of powertrains having an internal combustion engine, or other torsional vibration inducing prime mover coupled to a drivetrain that may include a fixed or selectable gearbox, transmission, and/or transaxle to power a machine or vehicle. The present invention is independent of the particular transmission technology and may be used with manual or automatic gear-change or speed-change transmissions, continuously variable transmissions (CVT's), and/or any combination or hybrid. The representative transversely mounted powertrain illustrated in FIG. 1 includes a multi-cylinder internal combustion engine 10 having a plurality of components that rotate during operation and create rotational inertia with a corresponding torque or moment that acts on stationary structure of an associated vehicle (not shown). Engine 10 generally represents any of a variety of internal combustion engines/motors that may include spark-ignition and compression-ignition engines and other prime movers particularly suited for vehicular applications. As previously described, the present invention may be utilized in various other types of engines and other prime movers that generate a vibrational reaction torque or moment associated with rotational acceleration or deceleration of various engine, motor, and/or transmission/powertrain components and is not limited to vehicular applications or internal combustion engines. Engine 10 typically includes one or more rotating components that may be considered the primary contributors to reaction torque transmitted through engine mounts to a vehicle chassis or other stationary structure due to the magnitude of rotational inertia of the components. For a typical internal combustion engine application, crankshaft 16 is a primary constituent of engine rotational inertia and the resulting reaction torque. Other components (not shown) whose angular acceleration may contribute to the reaction torque include a flywheel, connecting rods, harmonic damper, and camshaft(s), for example.

A device 20 couples crankshaft 16 of engine 10 to a rotating component of a transaxle or transmission 70, such as torque converter 30 or flywheel, for example. As illustrated and described in greater detail below, device 20 may be implemented by one or more gears, sprockets, gear sets, belts, or other cooperating components to reverse the direction of rotation of torque converter 30 relative to crankshaft 16. The actual implementation and positioning of device 20 may depend on various application specific considerations. For example, in transversely mounted powertrain applications, the implementation of device 20 may be dictated by packaging constraints such that the particular implementation does not significantly increase the transverse length of the engine/drivetrain. In various embodiments, device 20 may also increase or decrease rotational speed of torque converter 30 relative to crankshaft 16 to generally match the effective magnitude of rotational inertia produced by rotating components of transmission/transaxle 70 to that of engine 10. Depending upon the particular application and implementation, the speed differential may be fixed, continuously variable, or selectable from two or more predetermined ratios. For example, the device may be implemented by a gear-change transmission, speed-change transmission, or continuously variable transmission. Applications using a selectable or controllable speed differential may include either a mechanical, electrical, or microprocessor based controller to determine an appropriate speed differential for current operating conditions or a selected operating mode, for example.

As also illustrated in FIG. 1, torque converter 30 is connected to turbine shaft 40, which is coupled via chain drive 50 to input shaft 60 of transmission or transaxle 70. Left axle 80 and right axle 90 are connected to corresponding left and right vehicle wheels (not shown), or various auxiliary equipment for non-vehicular applications.

In operation, torque from engine 10 is carried by crankshaft 16 through coupling device 20 to torque converter 30, which provides a selective fluid coupling and torque multiplication under various operating conditions to turbine shaft 40. Chain drive 50 transfers torque from turbine shaft 40 and torque converter 30 through input shaft 60 to transaxle 70. Left axle 80 and right axle 90 receive power from transmission 70. Changes in rotational speed of various rotating components of engine 10, such as crankshaft 16, for example, result in a corresponding acceleration of rotational inertia and accompanying torque or moment. However, according to the present invention, the counter-rotation of various closely coupled transmission/transaxle or drive train components, such as torque converter 30, for example, results in a corresponding rotational acceleration of opposite hand or in the opposite direction which produces a torque or moment of opposite sense or direction that tends to reduce or cancel the torque or moment generated by the engine components. As such, the net vibrational torque reaction transmitted to the engine mounts or other stationary powertrain components, such as a vehicle chassis, is reduced or eliminated. The effective magnitudes of the rotational inertias generated by components associated with engine 10 and components associated with transmission or transaxle 70 may be adjusted via component mass and geometry as well as the relative rotational speed, which may be selected or determined by coupling device 20 as described herein.

A top-view block diagram illustrating a system or method for managing inertial torque reaction according to one embodiment of the present invention is shown in FIG. 2. In this embodiment, coupling device 20 is implemented by a spur gear or other toothed wheel 220 connected to an engine crankshaft 16 and in meshing engagement with one or more associated gears 210, implemented by a scissors gear in this example to reduce or eliminate backlash and associated gear rattle or noise. As best illustrated and described with reference to FIG. 3, coupling device 20 reverses rotational direction of torque converter 30 relative to the engine crankshaft. Depending upon the particular application and implementation, another device or a gear set may be used in place of scissors gear 210 to provide counter-rotation of one or more transmission or drive train components and reduce or eliminate backlash and any associated gear noise.

As shown in FIG. 2, scissors gear 210 is connected to torque converter 30, which, in turn, is fluidly coupled via operation of torque converter 30 to the turbine shaft or input shaft of transmission 70. The relative speed between the engine crankshaft and torque converter 30 may optionally be controlled or determined by the selected input/output ratio or gear ratio of coupling device 20. In one embodiment, the gear ratio of device 20 is selected so that torque converter 30 rotates at a speed based on rotational speed of the engine crankshaft to substantially match the effective magnitudes of rotational inertia of the forward rotating transmission components to the rearward rotating engine components. Substantially matching the effective magnitudes of rotational inertia associated with the transmission to the counter-rotating inertia associated with the engine reduces or eliminates any net torque reaction transferred to the stationary powertrain mounts or connections to surrounding structure, such as a vehicle chassis, due to vibrational changes in rotational speed (acceleration/deceleration) of the engine and transmission components. For internal combustion engine applications, each cylinder firing results in a small acceleration of the crankshaft and associated torque reaction that would otherwise be transmitted to the powertrain mounts if not offset by a corresponding acceleration in the opposite-rotating inertia, and its associated torque reaction, according to the present invention.

FIG. 3 is a side-view schematic block diagram illustrating a transversely mounted powertrain for a FWD vehicle shown in the top view of FIG. 2. In this embodiment, toothed wheel 220 is mounted concentrically on crankshaft axis 215 with its teeth meshing with scissors gear 210 mounted concentrically on the central axis of torque converter 30. The toothed wheel 220 and scissors gear 210 are meshing in such a way that they always rotate in opposite directions relative to each other. As shown in FIG. 3, during operation, toothed wheel 220 mounted to the crankshaft rotates in a counter-clockwise direction about crankshaft axis 215 in the same direction as the crankshaft. Scissors gear 210 is disposed to rotate in a direction opposite to that of toothed wheel 220. As such, scissors gear 210 rotates in a clockwise direction as shown in FIG. 3. Because scissors gear 210 is mounted on torque converter 30, torque converter 30 also rotates in the same direction as scissors gear 210. Thus, the meshing engagement of toothed wheel 220 and scissors gear 210 allows torque converter 30 to rotate in a clockwise direction when the crankshaft rotates in a counter-clockwise direction. With this reversal of rotational direction, the rotational accelerations of the inertia of torque converter 30 and associated transmission components act in an opposite direction to the rotational accelerations of the inertia of crankshaft 16 and associated engine components. The rotational acceleration of torque converter 30 acting in a direction opposite to that of crankshaft 16 will reduce or eliminate the resulting net torque reaction on stationary powertrain structure and hence improve performance with respect to noise, vibration, and harshness (NVH).

FIG. 4 is a top view schematic block diagram that illustrates another embodiment of the present invention for a longitudinally mounted powertrain, such as used in a typical rear wheel drive (RWD) vehicle, for example. In this embodiment, engine/motor 250 includes a crankshaft or output shaft coupled via device 255 to torque converter 260 of transmission 265 with output shaft 270 connected to a vehicle drive shaft (not shown) or other machinery depending upon the particular application. Torque from engine/motor 250 is carried by crankshaft 254 through coupling device 255 to torque converter 260. Coupling device 255 reverses the direction of rotation of torque converter 260 relative to crankshaft or engine/motor output shaft 254 so that one or more components of transmission 265, such as torque converter 260, provide a counter-rotating inertia to reduce or eliminate any net torque reaction associated with the rotating inertia of various components of engine/motor 250 on or through the stationary powertrain structure. Coupling device 255 may be implemented by any of a number of devices such as two or more meshing gears, a planetary gear set, or similar devices to reverse the direction of rotation. Coupling device 255 may include one or more components to reduce or eliminate backlash and any associated gear noise or rattle, such as a scissors gear, for example. Rotation of torque converter 260 provides a selective fluid coupling and torque multiplication so that power from torque converter 260 is transmitted through transmission 265 to transmission output shaft 270.

In addition to reversing the direction of rotation of various transmission components relative to rotating engine components, coupling device 255 may also provide a selected or selectable speed differential between motor/engine output shaft/crankshaft 254 and a transmission input shaft or torque converter 260 to substantially match the effective magnitudes of rotational inertia of rotating drive line and engine components. For applications utilizing a device 255 having a selectable speed differential, a corresponding mechanical, electrical, or microprocessor based actuator/controller may be provided to select one of the available input/output ratios based on an operating mode or current operating conditions, for example. Depending on the component mass and geometry, coupling device 255 may increase or decrease the rotational speed of one or more drive train components relative to one or more engine components. In one embodiment, coupling device 255 reduces the rotational speed of torque converter 260 relative to crankshaft 254 to better match effective rotational inertia magnitudes. However, the actual input/output speed of coupling device 255 will depend upon various application and implementation specific parameters including engine and drive train component geometry, relative mass of components, and relative location of rotating components, for example.

A cross-section of one embodiment of a device for coupling a prime mover to a drive train in a system or method for managing inertial torque reaction of a powertrain according to the present invention is shown in FIG. 5. In this embodiment, the coupling device comprises a planetary gear set to reverse rotational direction and provide a speed differential for a transmission/transaxle torque converter relative to an engine crankshaft. Appropriate construction of the planetary gear set provides a desired speed differential to substantially match effective magnitudes of rotational inertia of engine and drive train components as described herein.

As shown in FIG. 5, engine output shaft or crankshaft 254 is fastened to sun gear 320 using a plurality of fasteners 460. A plurality of fasteners 410 attach planet carrier 330 to a fixed, non-rotating portion of engine 110 (not shown), such as the engine block, for example. Flex plate 310 is attached to ring gear 350 using a plurality of fasteners 450. Torque converter 260 is attached to flex plate 310 using a plurality of fasteners 440. A plurality of planet gears 340 are constantly in mesh with ring gear 350 and sun gear 320. A plurality of needle bearings 370 supports each planet gear 340. The planet gears 340 and supporting needle bearings 370 are positioned inside planet carrier 330. Needle bearings 375 support ring gear 350 inside crankshaft 254 such that relative rotational motion is permitted between ring gear 350 and crankshaft 254. Thrust bearing 380 and thrust bushing 390 control the axial position of ring gear 350 between rear seal carrier 430 and planet carrier 330. Oil passage 360 supplies oil from the rear crankshaft main bearing of engine 110 to provide lubrication of the planetary gear set. Oil path 400 allows oil to drain out of the planetary gear set components and be returned to the engine oil sump. Oil seal 420 prevents loss of oil.

In operation, crankshaft 254 rotates in a first direction indicated generally by arrows 480. (Arrows 480 and 490 illustrate direction of rotation by use of the right hand rule where rotational direction is indicated by pointing the right-hand thumb in the direction of the straight arrow and closing the hand to make a fist such that the motion of the fingers indicates the direction of rotation.) Because sun gear 320 is attached to crankshaft 254 using a plurality of fasteners 460, sun gear 320 rotates in the same direction as crankshaft 254. Planet carrier 330 is rendered stationary by a plurality of fasteners 410 attaching it to a fixed, non-rotating portion of engine 110. Planet gears 340 are in mesh with sun gear 320 and rotate about their axes in a direction opposite to that of sun gear 320. Therefore the direction of rotation of planet gears 340, as generally indicated by arrow 490, is opposite that of crankshaft 254. Planet gears 340 are also in mesh with ring gear 350. The rotation of planet gears 340 forces ring gear 350 to rotate in the same direction, opposite to the crankshaft. Ring gear 350 is connected to flex plate 310 using a plurality of fasteners 450. As such, flex plate 310 also turns in the same direction as ring gear 350. Flex plate 310 is connected to torque converter 260 using a plurality of fasteners 440 forcing torque converter 260 to also rotate in the same direction. Thus torque converter 260 rotates in a direction opposite to that of crankshaft 254. The rotational inertia of torque converter 260 moving in a direction opposite to that of crankshaft 254 will reduce or eliminate the torque reaction induced by any acceleration of rotational inertia of crankshaft 254 on stationary powertrain structure and hence improve performance with respect to noise, vibration, and harshness (NVH).

A block diagram illustrating a system and method for managing inertial torque reaction according to one embodiment of the present invention in a hybrid powertrain is shown in FIG. 6. Hybrid powertrain 500 includes a multiple cylinder internal combustion engine 502 with an output shaft or crankshaft 504 coupled to a drive train 506. A one-way clutch 560 prevents crankshaft/output shaft 504 from reversing rotational direction. During selected operating modes of the hybrid system when engine 502 is operating to drive generator 510, device 508 reverses direction of rotation and provides a speed differential between output shaft 504 and generator 510, which is one of the more significant contributors to rotational inertia of drive train 506. As such, counter-rotation of generator 510 relative to crankshaft 504 reduces or eliminates any associated net torque reaction on stationary powertrain structure as described herein. In the representative embodiment illustrated in FIG. 6, device 508 is implemented by a planetary gear set with engine crankshaft 504 driving ring gear 520. Sun gear 522 is in constant meshing engagement with a plurality of planet gears 524 supported by carrier 526. Planet gears 524 are also in meshing engagement with ring gear 520.

Carrier 526 of device 508 is coupled via meshing engagement of gears 530, 532, and 534 to motor shaft 536 of electric motor 538. Gear 532 is coupled to intermediate shaft 540, which is in turn coupled to gear 542, which is in meshing engagement with output gear 544 coupled to output shaft 546. A battery 550 or other energy storage device is coupled via electrical connection 552 to motor 538 and generator 510.

According to the present invention, hybrid powertrain 500 includes one or more operating modes where one or more inertial components of engine 502 and powertrain 506 rotate in opposite directions to provide counter-rotating inertia to reduce or eliminate reaction torque associated with acceleration/deceleration of rotating components. When the vehicle speed is low, so that the rotational speed of planet carrier 526 is substantially less than that of crankshaft 504, sun gear 522 and generator 510 are forced to rotate in the direction opposite to that of the crankshaft. Depending upon the effective magnitude of rotational inertias of engine components and drive train components, the present invention may also provide a predetermined or selectable speed differential to substantially match effective magnitude of inertias as previously described.

While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims. 

1. A method for managing inertial torque reaction in a vehicle having an engine and a drive train, the method comprising: operating the drive train to rotate inertia in a direction opposite to rotating inertia created by operation of the engine.
 2. The method of claim 1 wherein the engine includes a crankshaft and the drive train includes a transmission having at least one inertial component including one of a torque converter and a flywheel and wherein the step of operating the drive train comprises rotating the at least one inertial component in a direction opposite to rotational direction of the crankshaft.
 3. The method of claim 1 further comprising coupling the drive train to the engine using a device to reverse direction of rotation of a drive train torque converter relative to an engine crankshaft.
 4. The method of claim 3 wherein the step of coupling comprises coupling the torque converter and the crankshaft using a planetary gear set.
 5. The method of claim 3 wherein the step of coupling comprises connecting the torque converter to the crankshaft using a plurality of toothed wheels.
 6. The method of claim 5 wherein at least one of the toothed wheels comprises a scissors gear.
 7. The method of claim 1 further comprising operating the drive train to create rotating inertia having a magnitude substantially equal to rotating inertia of the engine.
 8. The method of claim 1 further comprising operating at least one drive train component at a speed differential relative to engine speed, the speed differential being based on rotational inertia magnitude of the engine relative to rotational inertia magnitude of the drive train.
 9. The method of claim 1 wherein the step of operating the drive train comprises reducing speed of a transmission torque converter relative to an engine crankshaft.
 10. A method for managing inertial torque reaction in a powertrain having a prime mover and a drive train, the method comprising coupling the prime mover to the drive train using a device that reverses direction of rotation of a drive train inertial component relative to direction of rotation of a prime mover output component.
 11. The method of claim 10 further comprising operating the drive train inertial component at a speed differential relative to the prime mover output component, the speed differential based on rotational inertia associated with selected components of the prime mover relative to rotational inertia associated with selected components of the drive train.
 12. The method of claim 10 wherein the step of coupling comprises coupling a torque converter of the drive train to a crankshaft of the prime mover using a planetary gear set.
 13. The method of claim 10 wherein the step of coupling comprises coupling a torque converter of the drive train to a crankshaft of the prime mover using a first gear secured to the crankshaft in meshing engagement with a second gear secured to the torque converter.
 14. The method of claim 10 wherein the step of coupling comprises coupling a generator of the drive train to a crankshaft of the prime mover using a planetary gear set.
 15. A system for managing inertial torque reaction in a vehicle having a powertrain including a prime mover and a drive train, the system comprising a device for coupling the prime mover to the drive train such that the drive train generates a rotational inertia reaction torque in a direction opposite rotational inertia reaction torque generated by the prime mover.
 16. The system of claim 15 wherein the device comprises: a first gear secured for rotation with an output component of the prime mover; and a second gear in meshing engagement with the first gear and secured for rotation with an input component of the drive train such that the input component of the drive train rotates in an opposite direction relative to rotation of the output component of the prime mover.
 17. The system of claim 15 wherein the device comprises a planetary gear set.
 18. The system of claim 15 wherein the device creates a speed differential between rotational speed of an output component of the prime mover and an input component of the drive train.
 19. The system of claim 15 wherein the prime mover includes a crankshaft, the drive train includes a transmission having a torque converter, and wherein the device comprises a gear set coupling the crankshaft to the torque converter.
 20. The system of claim 15 wherein the prime mover includes a crankshaft, the drive train includes a transmission having a torque converter, and wherein the device reverses direction of rotation of the torque converter relative to direction of rotation of the crankshaft.
 21. A system for reducing vibration associated with operation of a vehicle, the system comprising: a prime mover having an output component that rotates during operation; a transmission having an input component; and a device for coupling the output component of the prime mover to the input component of the transmission so that the input component rotates in a direction opposite to the output component of the prime mover.
 22. The system of claim 21 wherein the device comprises a plurality of gears.
 23. The system of claim 21 wherein the transmission comprises an automatic transmission transversely mounted in the vehicle and wherein the input component comprises a torque converter.
 24. The system of claim 21 wherein the transmission comprises an automatic transmission longitudinally mounted in the vehicle and wherein the input component comprises a torque converter.
 25. The system of claim 21 wherein device creates a speed differential between rotational speed of the output component of the prime mover and the input component of the transmission.
 26. The system of claim 25 wherein the speed differential is based on rotational inertia of the prime mover relative to rotational inertia of the transmission. 